1. Field of the Invention
The present invention relates to a magnetic resonance (“MR”) catheter antenna and method of using the same.
2. Discussion of the Related Art
The advantageous use of magnetic resonance technology in provided safe, rapid images of an internal portion of a patient has long been known. But to obtain an image of a vessel within the body, it is necessary to introduce an invasive probe within that vessel. To provide an MR image, the probe has a receiving coil therein. RF pulses are provided to the region of interest to excite magnetic resonance signals. Gradient magnetic pulses are applied to the region of interest with the receiver coil receiving magnetic resonance signals and emitting responsive output signals, which may be processed by a computer to provide image information for display in a desired manner.
To image even the smallest internal passageways, such as, for example, arteries emanating from the heart, it is necessary to employ a flexible receiver coil. In addition, the probe should have a very small outer diameter so that it may be inserted inside the artery so that a magnetic resonance image thereof can be obtained.
U.S. Pat. No. 5,699,801 to Atalar et al. discloses a receiver 8 that it is in the form of coil 22. Coil 22 has a pair of electrodes 24, 26 that are generally parallel and are spaced apart from each other. The electrodes 24, 26 are embedded in a dielectric material 30, and the ends of the conductors 24, 26 are electrically connected by wire 32. Coil 22 is disclosed as a having a width D of about 0.5 to 2.0 cm. The conductors 24, 26 have an individual diameter of about 0.1 mm to 3 mm. Thus, coil 22 is embedded in a dielectric material 30 (i.e., TEFLON®), which requires that the practical diameter of any coil built in accordance with the teachings of the '801 patent will have a diameter that is too large to be placed in relatively small arteries adjacent to the heart. In accordance with the teachings of the '801 patent, the dielectric material 30 should be resilient to permit flexing of the coil so that it will return to its original position. Thus, the probe will place stress and may perforate through an artery wall as it returns to its original position. The dielectric material 30 must be sufficiently rigid to resist undesired deformation of the spacing D between the conductors 24, 26. Thus, the coil will not be flexible enough to be guided through these arteries.
There still exists a need in the art to provide a probe that can be sized to fit within relatively small arteries so that an MR image of these vessels can be obtained. There still further exists a need for a probe that can be guided with a guide wire while being insertable into these arteries to facilitate the insertion of the probe into these arteries.